全文获取类型
收费全文 | 7162篇 |
免费 | 314篇 |
国内免费 | 283篇 |
专业分类
电工技术 | 104篇 |
综合类 | 507篇 |
化学工业 | 764篇 |
金属工艺 | 2103篇 |
机械仪表 | 1014篇 |
建筑科学 | 168篇 |
矿业工程 | 78篇 |
能源动力 | 43篇 |
轻工业 | 558篇 |
水利工程 | 21篇 |
石油天然气 | 50篇 |
武器工业 | 36篇 |
无线电 | 897篇 |
一般工业技术 | 461篇 |
冶金工业 | 643篇 |
原子能技术 | 47篇 |
自动化技术 | 265篇 |
出版年
2023年 | 46篇 |
2022年 | 109篇 |
2021年 | 145篇 |
2020年 | 135篇 |
2019年 | 109篇 |
2018年 | 116篇 |
2017年 | 175篇 |
2016年 | 143篇 |
2015年 | 211篇 |
2014年 | 417篇 |
2013年 | 413篇 |
2012年 | 496篇 |
2011年 | 471篇 |
2010年 | 360篇 |
2009年 | 364篇 |
2008年 | 353篇 |
2007年 | 511篇 |
2006年 | 466篇 |
2005年 | 450篇 |
2004年 | 388篇 |
2003年 | 360篇 |
2002年 | 315篇 |
2001年 | 276篇 |
2000年 | 249篇 |
1999年 | 134篇 |
1998年 | 117篇 |
1997年 | 104篇 |
1996年 | 61篇 |
1995年 | 78篇 |
1994年 | 59篇 |
1993年 | 34篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有7759条查询结果,搜索用时 328 毫秒
1.
2.
3.
《Contact lens & anterior eye》2021,44(6):101388
PurposeTo investigate the relationship between the real contact lens imprint into the conjunctival tissue, observed by optical coherence tomography (OCT) and conjunctival staining and contact lens wearing comfort.Methods17 participants (mean age = 26.6 SD ± 3.6 years; 7 females) were fitted with three different contact lenses base curves of the same silicone hydrogel custom lens type (Visell 50; Hecht Contactlinsen, Au, Germany) in a randomised order. One lens was optimally fitted according to the manufacturer's recommendation, one fitted 0.4 mm flatter and one fitted 0.4 mm steeper. After 4 h of lens wear the contact lens edge in the area of the conjunctiva was imaged nasally and temporally using OCT (Optovue iVue SD-OCT). To correct the artefact due to optical distortion with OCT, the imprint of all worn lenses was measured on a glass plate afterwards. Conjunctival staining in the limbal region after 4 h of lens wear was classified using the CCLRU Grading Scale. Comfort scoring was based on visual analog scales from 0 (very poor) to 100 (excellent).ResultsThe mean conjunctival imprint of all contact lens edges was 32.0 ± 8.1 μm before and 7.3 ± 6.5 μm after distortion correction of the OCT images. The distortion corrected conjunctival imprint with the 0.4 mm steeper lens (11.5 ± 6.2 μm) was statistically significantly greater compared to the optimally fitted lens (6.5 ± 5.9 μm) (One-way ANOVA followed Tukey-test; p = 0.017) and greater compared to the 0.4 mm flatter lens (3.9 ± 5.3 μm) (p < 0.001). There was no statistically significant difference between the optimally fitted lens and the 0.4 mm flatter lens (p = 0.209). The nasally measured imprint (11.4 ± 9.0 μm) was significantly greater than the temporally measured (3.3 ± 7.6 μm) (p < 0.001). There was no statistically significant correlation between the amount of conjunctival imprint and the graded conjunctival staining (p = 0.346) or the wearer’s comfort (p = 0.735).ConclusionsContact lens edges imaged by OCT exhibited displacement artefacts. The observed conjunctival imprints are a combination of real conjunctival compression and artefacts. A deeper imprint of the contact lens into the conjunctiva caused by a steeper base curve was not related to clinically significant staining or changes in comfort after 4 h of lens wear. The observed differences between nasal and temporal imprint are likely to be caused by variations of conjunctival thickness and the shape of the underlying sclera. 相似文献
4.
1 Introduction High power laser diode arrays (LDA) have many advan- tages such as small volume, long working life, high slope efficiency and high optical density, so they have many applications in medical treatment, material pro- cessing, and for the pumping source of solid laser and etc. But unfortunately, the LDA can not be easy to use directly in these fields because of their poor beam quality and extremely asymmetric divergent beams (!x≈ 5°~10°and !y≈20°~35°, for example), so it … 相似文献
5.
通过对三重四极透镜成像系统的渐晕模拟,研究了并行电子能量损失谱仪中物方视场、漂移管径以及与电荷耦合探测器(CCD)幅面尺寸的对应关系,并由它们间的相互关系确定了与CCD幅面二维探测器尺寸相匹配的漂移管径。 相似文献
6.
7.
8.
9.
论述了电磁铁铁芯 (硅钢片 )模具的设计要点及其线切割加工的技巧 ,提出了提高模具加工精度和使用寿命的有效措施。 相似文献
10.
介绍了大方坯连铸机离线设备对中台及样规的改进方案.改进后,大大缩短了设备检修时间,降低了工人的劳动强度. 相似文献